// SPDX-License-Identifier: GPL-2.0-only
#define pr_fmt(fmt) "IPVS: " fmt

#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <asm/string.h>
#include <linux/kmod.h>
#include <linux/sysctl.h>

#include <net/ip_vs.h>

/* IPVS pe list */
static LIST_HEAD(ip_vs_pe);

/* semaphore for IPVS PEs. */
static DEFINE_MUTEX(ip_vs_pe_mutex);

/* Get pe in the pe list by name */
struct ip_vs_pe *__ip_vs_pe_getbyname(const char *pe_name)
{
        struct ip_vs_pe *pe;

        IP_VS_DBG(10, "%s(): pe_name \"%s\"\n", __func__,
                  pe_name);

        rcu_read_lock();
        list_for_each_entry_rcu(pe, &ip_vs_pe, n_list) {
                /* Test and get the modules atomically */
                if (pe->module &&
                    !try_module_get(pe->module)) {
                        /* This pe is just deleted */
                        continue;
                }
                if (strcmp(pe_name, pe->name)==0) {
                        /* HIT */
                        rcu_read_unlock();
                        return pe;
                }
                module_put(pe->module);
        }
        rcu_read_unlock();

        return NULL;
}

/* Lookup pe and try to load it if it doesn't exist */
struct ip_vs_pe *ip_vs_pe_getbyname(const char *name)
{
        struct ip_vs_pe *pe;

        /* Search for the pe by name */
        pe = __ip_vs_pe_getbyname(name);

        /* If pe not found, load the module and search again */
        if (!pe) {
                request_module("ip_vs_pe_%s", name);
                pe = __ip_vs_pe_getbyname(name);
        }

        return pe;
}

/* Register a pe in the pe list */
int register_ip_vs_pe(struct ip_vs_pe *pe)
{
        struct ip_vs_pe *tmp;

        /* increase the module use count */
        if (!ip_vs_use_count_inc())
                return -ENOENT;

        mutex_lock(&ip_vs_pe_mutex);
        /* Make sure that the pe with this name doesn't exist
         * in the pe list.
         */
        list_for_each_entry(tmp, &ip_vs_pe, n_list) {
                if (strcmp(tmp->name, pe->name) == 0) {
                        mutex_unlock(&ip_vs_pe_mutex);
                        ip_vs_use_count_dec();
                        pr_err("%s(): [%s] pe already existed "
                               "in the system\n", __func__, pe->name);
                        return -EINVAL;
                }
        }
        /* Add it into the d-linked pe list */
        list_add_rcu(&pe->n_list, &ip_vs_pe);
        mutex_unlock(&ip_vs_pe_mutex);

        pr_info("[%s] pe registered.\n", pe->name);

        return 0;
}
EXPORT_SYMBOL_GPL(register_ip_vs_pe);

/* Unregister a pe from the pe list */
int unregister_ip_vs_pe(struct ip_vs_pe *pe)
{
        mutex_lock(&ip_vs_pe_mutex);
        /* Remove it from the d-linked pe list */
        list_del_rcu(&pe->n_list);
        mutex_unlock(&ip_vs_pe_mutex);

        /* decrease the module use count */
        ip_vs_use_count_dec();

        pr_info("[%s] pe unregistered.\n", pe->name);

        return 0;
}
EXPORT_SYMBOL_GPL(unregister_ip_vs_pe);